1. Field of Invention
The invention relates to a stylus and a method of manufacturing the same, and more particularly to a self-aligned stylus with high sphericity and a method of manufacturing the same.
2. Related Art
The trend towards miniaturization and modularization in manufacturing has led to a requirement for a coordinate measuring machine (CMM) capable of measuring tiny features on small components. Surface profilers, micro coordinate measurement machines (μCMMS), and scanning probe microscopes (SPMs) have been developed to measure three dimensional coordinates of structures from nanometer to micrometer scales. As for the high-precision micro-metrology, in order to measure three-dimensional features, such as deep trenches, sidewalls and nozzles, having the high aspect ratio, it is also necessary to use micro-spherical scanning probes which are accurately fabricated for high sphericity. In the μCMM field, spherical pellets with diameters ranging from hundreds nanometers to tens micrometers are commonly attached on the micro-probes.
In practical μCMM applications, any angular orientation variation between an object and the measurement reference component may result in so-called “Abbe error” in measuring the linear displacement or the spatial dimension of the object. From Abbe error theory, the sphericity of these spherical styluses and the alignment between the contact sphere and the stylus pin are the key roles in the μCMM accuracy.
The wire electro-discharge grinding (WEDG) technology has been developed to fabricate the vibroscanning probe. By combining the WEDG with one pulse electro-discharge, a burnished micro-spherical probe with 40 μm diameter has been fabricated.
FIG. 12 is a pictorial view showing a conventional stylus. Referring to FIG. 12, the conventional stylus includes a substrate 150, a stylus pin 152 and a sphere 110. The stylus pin 152 is connected to the substrate 150 and the sphere 110. The stylus fabricated by way of WEDG has many drawbacks. For example, the sphericity of the sphere 110 is not high, the sphere 110 is not well aligned with the stylus pin 152, and the surface of the sphere 110 is very rough. These drawbacks make the measured result of the μCMM system become inaccurate. In addition, the sphere 110, the substrate 150 and the stylus pin 152 have to be made of conductors, and cannot isolate charges and heat of the object in some occasions.
Thus, it is an important subject of the invention to provide a stylus, which has high sphericity, a well aligned state and a smooth surface.